The present invention is directed to underwater excavation, and in particular to tunneling under the floor of a body of water.
Difficulties in financing large capital projects arise not only from the large amounts of capital involved but also, particularly in times of high interest, from the delay between the commitment of the capital and the time when the project begins to produce revenue. As a consequence, any method for reducing this delay has the effect of reducing the cost of the project.
Among the very large capital projects are tunnels such as that proposed to run beneath the English Channel. The amount of capital to be committed is considerable, but revenue will not be generated by the tunnel until the work is finished. The commitment of the capital is thus more readily justified if the time required for construction can be reduced. One way to reduce construction time is to tunnel from both ends, rather than one.
It is an object of the present invention to further reduce construction time by beginning the tunnel not only at both ends, but also at some point between the ends, i.e., underwater. Another object is to carry out the underwater excavation without unduly disrupting water traffic above the point of penetration of the floor of the body of water. It is a further object to provide an underwater excavation work chamber that has a breathable atmosphere, yet permits easy entry and exit to and from the chamber.